The present invention relates in general to a mechanical, demand-type, paper sheet feeder for feeding pre-cut sheets of paper or envelopes from different paper trays into a rotating printer platen. More specifically, the paper sheet feeder includes various feed rollers associated with the different paper trays, which paper trays are constructed to facilitate storage of stacks of individual sheets of paper having different widths by a simple adjustment of the spaced apart relationship between a pair of lateral paper supporting members. In this regard, the lateral paper supporting members are arranged in operative association with a control rod to facilitate the replenishment of paper in the stack, while maintaining the top sheet of paper within the stack in engagement with the various feed rollers for feeding sheets of paper and envelopes into the rotating printer platen.
Tremendous advances have been made in the last few years in automating office procedures. Conventional typewriters have grown into mini-computers for performing word processing, storage and other functions. The speed at which these machines produce words on paper is increasing at a rapid rate. As added speed and sophistication are developed into such machines, the actual putting of words onto paper becomes ancillary to the main function of collecting and organizing the information into a format to be printed. In order to have flexibility and speed, many systems have been developed where an operator manipulates words on a cathode ray tube or other word processing equipment until the final copy is in the format desired. With all of these advantages, it has developed that today one of the major bottlenecks in terms of time, and therefore usefulness of this equipment, is the rate at which paper can be brought to and moved past a printing head to produce the final hard copy.
Of course, it is possible to use continuous sheets of perforated paper, as is commonly done in computer applications, having sprocket holes along the sides thereof to continuously feed and move the paper through an impact printer. This, however, requires special paper which is not suitable to the many requirements for which normal typewriting is employed.
Many machines exist, both copying machines and printing machines, which automatically feed paper past a printing or reproducing station. These machines are normally run synchronously such that prior to the time the paper is fed, the information to be printed on the paper is already organized and the papers move past the printing head in a continuous fashion. This is not generally suitable for impact printing devices, since impact printing is accomplished with the paper stationary rather than moving, and further the adaption of normal typewriting type printing requires moving of paper not only in an intermittent basis, but also in the forward and reverse direction in accordance with the information to be typed. Still further, with such existing equipment, it is generally not possible to manually feed separate sheets of paper, which may be of different size or thickness such as, for example, envelopes, without disconnecting the equipment from the printing machine.
In U.S. Pat. No. 4,326,815, which patent is assigned to the same assignee of the present invention, there is disclosed a paper sheet feeding apparatus, including a removable paper tray, which is capable of being retrofitted with respect to existing printing devices, i.e., distributed as an after market product, as well as being capable of being sold and distributed with the printing device. The retrofit characteristic of this paper sheet feeding apparatus lends itself to conform to the climate of the existing impact printing devices, rather than requiring the radical modification thereof, so as to conform with the needs of high speed paper feeding. Although the known paper sheet feeding apparatus has been commercially successful, such apparatus requires the use of dedicated paper trays for each different width or size of paper being used. This necessitates the removal of one paper tray and its replacement with a paper tray of a different size if paper having a different width is desired. As such, one must maintain, on hand, an inventory of paper trays of varying size to accommodate the different needs of the user.
Another paper feeding apparatus adapted to be retrofitted onto an existing printing device is known from U.S. Pat. No. 4,544,294. In accordance with this known paper sheet feeding apparatus, a pair of spaced apart rocker plates having a flat bottom support the lateral sides of a stack of individual sheets of paper. The rocker plates are slideable relative with respect to each other along a cross rod, as well as being rotatable or pivotable thereabout, so as to accommodate stacks of sheets of paper of different widths. However, as the rocker plates are spaced apart, the central portion of the stack remains unsupported and often sags, which can have the tendency to cause individual sheets of paper to be misfed. In addition, the requirement that the entire rocker plate be rotatable or pivotable about the cross rod for engaging the upper sheet of paper of the stack with its associated paper feed rollers, results in a construction which is relatively complicated to assemble, as well as to perform periodic maintenance. Another paper sheet feeding apparatus of the latter type is known from U.S. Pat. No. 1,914,849.
Accordingly, it can be appreciated that there is an unsolved need for a paper tray for a printing device which readily accommodates stacks of individual sheets of paper having different widths or size and which is simple in construction to facilitate assembly and the maintenance thereof.